{
  "id": "markup.invalid_json",
  "category": "request_validation",
  "summary": "The reply_markup argument is not valid JSON.",
  "match_any": [
    {
      "error_code": 400,
      "description_exact": "Bad Request: can't parse reply keyboard markup JSON object"
    }
  ],
  "scope": {
    "method_examples": [
      "sendMessage",
      "editMessageReplyMarkup"
    ],
    "exhaustive": false
  },
  "possible_causes": [
    "A nonempty reply_markup argument failed JSON decoding."
  ],
  "diagnostic_limits": "Valid JSON with the wrong shape or invalid button fields produces different errors.",
  "evidence": [
    {
      "source": "server-10.3",
      "path": "telegram-bot-api/Client.cpp",
      "lines": [
        10504,
        10518
      ],
      "note": "The reply_markup parser emits this literal only when JSON decoding fails."
    },
    {
      "source": "server-10.3",
      "path": "telegram-bot-api/Client.cpp",
      "lines": [
        13800,
        13803
      ],
      "note": "Method validation errors are passed to the response normalizer."
    },
    {
      "source": "server-10.3",
      "path": "telegram-bot-api/Client.cpp",
      "lines": [
        165,
        205
      ],
      "note": "Adds the code-specific prefix and lowercases only the initial character of ordinary messages."
    }
  ],
  "example": {
    "method": "sendMessage",
    "response": {
      "ok": false,
      "error_code": 400,
      "description": "Bad Request: can't parse reply keyboard markup JSON object"
    }
  },
  "evidence_level": "source_derived",
  "guidance": {
    "action": "correct_reply_markup_json",
    "repeat_request": "after_relevant_change",
    "preconditions": [
      "Serialize reply_markup as a JSON object with the structure required by the selected keyboard type."
    ]
  }
}